Can a tumor marker test alone diagnose cancer?

A tumor marker test is usually not used by itself to diagnose cancer. According to the National Cancer Institute, tumor markers can help diagnose cancer, but having an elevated level of a tumor marker does not mean that someone has cancer.

There are two reasons a single result is not enough. First, noncancerous conditions can sometimes cause a tumor marker level to rise. Second, not everyone with a particular type of cancer will have a higher level of the marker associated with that cancer.

Because of this, the NCI explains that measurements of tumor markers are usually combined with the results of other tests, such as biopsies or imaging, to diagnose cancer. In other words, a marker is one piece of information that a health care team weighs alongside other results.

If you are wondering what a specific tumor marker result means for you, your health care team can explain how it fits with your other tests. They can say more than a single number can.